#include<iostream>
#include<cmath>

using namespace std;

double root(double x, double y) {
    if (x >= y) {
        return sqrt(x - y);
    } else {
        return 0;
    }
}

int main() {
    double a, b;
    cin >> a >> b;
    cout << root(a, b) << endl;
    return 0;
}
